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1. Habitat use as indicator of adaptive capacity to climate change

   https://doi.org/10.1111/ddi.13223  

   Teitelbaum, Claire S. ; Sirén, Alexej P. K. ; Coffel, Ethan ; Foster, Jane R. ; Frair, Jacqueline L. ; Hinton, Joseph W. ; Horton, Radley M. ; Kramer, David W. ; Lesk, Corey ; Raymond, Colin ; et al ( January 2021 , Diversity and Distributions)

   Populations of cold‐adapted species at the trailing edges of geographic ranges are particularly vulnerable to the negative effects of climate change from the combination of exposure to warm temperatures and high sensitivity to heat. Many of these species are predicted to decline under future climate scenarios, but they could persist if they can adapt to warming climates either physiologically or behaviourally. We aim to understand local variation in contemporary habitat use and use this information to identify signs of adaptive capacity. We focus on moose (Alces alces), a charismatic species of conservation and public interest.

   The northeastern United States, along the trailing edge of the moose geographic range in North America.

   We compiled data on occurrences and habitat use of moose from remote cameras and GPS collars across the northeastern United States. We use these data to build habitat suitability models at local and regional spatial scales and then to predict future habitat suitability under climate change. We also use fine‐scale GPS data to model relationships between habitat use and temperature on a daily temporal scale and to predict future habitat use.

   We find that habitat suitability for moose will decline under a range of climate change scenarios. However, moose across the region differ in their use of climatic and habitat space, indicating that they could exhibit adaptive capacity. We also find evidence for behavioural responses to weather, where moose increase their use of forested wetland habitats in warmer places and/or times.

   Our results suggest that there will be significant shifts in moose distribution due to climate change. However, if there is spatial variation in thermal tolerance, trailing‐edge populations could adapt to climate change. We highlight that prioritizing certain habitats for conservation (i.e., thermal refuges) could be crucial for this adaptation.

    

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2. Winter Tick Burdens for Moose Are Positively Associated With Warmer Summers and Higher Predation Rates

   https://doi.org/10.3389/fevo.2021.758374  

   Hoy, Sarah R. ; Vucetich, Leah M. ; Peterson, Rolf O. ; Vucetich, John A. ( November 2021 , Frontiers in Ecology and Evolution)

   Climate change is expected to modify host-parasite interactions which is concerning because parasites are involved in most food-web links, and parasites have important influences on the structure, productivity and stability of communities and ecosystems. However, the impact of climate change on host–parasite interactions and any cascading effects on other ecosystem processes has received relatively little empirical attention. We assessed host-parasite dynamics for moose ( Alces alces ) and winter ticks ( Dermacentor albipictus ) in Isle Royale National Park over a 19-year period. Specifically, we monitored annual tick burdens for moose (estimated from hair loss) and assessed how it covaried with several aspects of seasonal climate, and non-climatic factors, such as moose density, predation on hosts by wolves ( Canis lupus ) and wolf abundance. Summer temperatures explained half the interannual variance in tick burden with tick burden being greater following hotter summers, presumably because warmer temperatures accelerate the development of tick eggs and increase egg survival. That finding is consistent with the general expectation that warmer temperatures may promote higher parasite burdens. However, summer temperatures are warming less rapidly than other seasons across most regions of North America. Therefore, tick burdens seem to be primarily associated with an aspect of climate that is currently exhibiting a lower rate of change. Tick burdens were also positively correlated with predation rate, which could be due to moose exhibiting risk-sensitive habitat selection (in years when predation risk is high) in such a manner as to increases the encounter rate with questing tick larvae in autumn. However, that positive correlation could also arise if high parasite burdens make moose more vulnerable to predators or because of some other density-dependent process (given that predation rate and moose density are highly correlated). Overall, these results provide valuable insights about interrelationships among climate, parasites, host/prey, and predators. 

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3. AVAILABILITY AND USE OF MOOSE BROWSE IN RESPONSE TO POST-FIRE SUCCESSION ON KANUTI NATIONAL WILDLIFE REFUGE, ALASKA

   Julianus, E. ( August 2019 , Alces)

   null (Ed.)

   Wildfire is a prominent landscape-level disturbance in interior Alaska and associated vegetation changes affect quantity and quality of moose (Alces alces) habitat. These changes are important to land and wildlife managers responsible for managing habitat and ensuring sustained yield of game species such as moose. Considering the changing fire regime related to climate change, we explored post-fire dynamics of moose habitat to broaden understanding of local habitat characteristics associated with wildfire on the Kanuti National Wildlife Refuge in interior Alaska. We studied 34 sites in different aged stands (2005 burn, 1990 burn, 1972 burn, and unburned in the last 80 years) in August 2012 and 2013 to estimate summer browse density, biomass production, and browse use, and revisited each site the following March to estimate winter browse availability and offtake. We also used location data from 51 radio-collared moose to quantify use of burns on the Kanuti National Wildlife Refuge. We found that summer density and biomass of preferred browse was highest at sites in the 1990 burn, although use of burns varied seasonally. Despite high biomass in the most recent 2005 burn, radio-collared moose avoided burns <11 years old in summer and had preference for older stands (>30 years old). Winter browse offtake was highest in the 1990 and 1972 burns despite relatively high biomass available in the 2005 burn. The disparate use of burns, particularly low use of the 2005 burn, likely reflected a combination of influences including species composition and preference, predator avoidance strategies, a low density moose population, and historic moose distribution patterns. 

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4. Negative frequency‐dependent foraging behaviour in a generalist herbivore ( Alces alces ) and its stabilizing influence on food web dynamics

   https://doi.org/10.1111/1365-2656.13031  

   Hoy, Sarah R. ; Vucetich, John A. ; Liu, Rongsong ; DeAngelis, Don L. ; Peterson, Rolf O. ; Vucetich, Leah M. ; Henderson, John J. ; Street, ed., Garrett ( July 2019 , Journal of Animal Ecology)

   Resource selection is widely appreciated to be context‐dependent and shaped by both biological and abiotic factors. However, few studies have empirically assessed the extent to which selective foraging behaviour is dynamic and varies in response to environmental conditions for free‐ranging animal populations.

   Here, we assessed the extent that forage selection fluctuated in response to different environmental conditions for a free‐ranging herbivore, moose (Alces alces), in Isle Royale National Park, over a 10‐year period. More precisely, we assessed how moose selection for coniferous versus deciduous forage in winter varied between geographic regions and in relation to (a) the relative frequency of forage types in the environment (e.g. frequency‐dependent foraging behaviour), (b) moose abundance, (c) predation rate (by grey wolves) and (d) snow depth. These factors are potentially important for their influence on the energetics of foraging. We also built a series of food‐chain models to assess the influence of dynamic foraging strategies on the stability of food webs.

   Our analysis indicates that moose exhibited negative frequency dependence, by selectively exploiting rare resources. Frequency‐dependent foraging was further mediated by density‐dependent processes, which are likely to be predation, moose abundance or some combination of both. In particular, frequency dependence was weaker in years when predation risk was high (i.e. when the ratio of moose to wolves was relatively low). Selection for conifers was also slightly weaker during deep snow years.

   The food‐chain analysis indicates that the type of frequency‐dependent foraging strategy exhibited by herbivores had important consequences for the stability of ecological communities. In particular, the dynamic foraging strategy that we observed in the empirical analysis (i.e. negative frequency dependence being mediated by density‐dependent processes) was associated with more stable food web dynamics compared to fixed foraging strategies.

   The results of this study indicated that forage selection is a complex ecological process, varying in response to both biological (predation and moose density) and abiotic factors (snow depth) and over relatively small spatial scales (between regions). This study also provides a useful framework for assessing the influence of other aspects of foraging behaviour on the stability of food web dynamics.

    

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5. Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti

   https://doi.org/10.1111/gcb.17041  

   Dennington, Nina L. ; Grossman, Marissa K. ; Ware‐Gilmore, Fhallon ; Teeple, Janet L. ; Johnson, Leah R. ; Shocket, Marta S. ; McGraw, Elizabeth A. ; Thomas, Matthew B. ( November 2023 , Global Change Biology)

   Most models exploring the effects of climate change on mosquito‐borne disease ignore thermal adaptation. However, if local adaptation leads to changes in mosquito thermal responses, “one size fits all” models could fail to capture current variation between populations and future adaptive responses to changes in temperature. Here, we assess phenotypic adaptation to temperature inAedes aegypti, the primary vector of dengue, Zika, and chikungunya viruses. First, to explore whether there is any difference in existing thermal response of mosquitoes between populations, we used a thermal knockdown assay to examine five populations ofAe. aegypticollected from climatically diverse locations in Mexico, together with a long‐standing laboratory strain. We identified significant phenotypic variation in thermal tolerance between populations. Next, to explore whether such variation can be generated by differences in temperature, we conducted an experimental passage study by establishing six replicate lines from a single field‐derived population ofAe. aegyptifrom Mexico, maintaining half at 27°C and the other half at 31°C. After 10 generations, we found a significant difference in mosquito performance, with the lines maintained under elevated temperatures showing greater thermal tolerance. Moreover, these differences in thermal tolerance translated to shifts in the thermal performance curves for multiple life‐history traits, leading to differences in overall fitness. Together, these novel findings provide compelling evidence thatAe. aegyptipopulations can and do differ in thermal response, suggesting that simplified thermal performance models might be insufficient for predicting the effects of climate on vector‐borne disease transmission.

    

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